The GOP selected Sarah Palin as its VP to stoke its base, but expanding that base should be the partys goal.

In the wake of the Republican defeat, there has been much recrimination and finger-pointing over tactics and strategy. Was the Sarah Palin choice fatal? Should John McCain have suspended his campaign during the financial crisis?

But the larger issue is whether 2008 was a “realigning election” that went deeper than the candidates or the current issues. The jury is still out as to whether Democrats can turn one sweeping victory into a generation-long dominance of the White House. A key element in a possible structural shift favoring Democrats is the changing demographics of the electorate. The U.S. is growing bigger, increasingly diverse and more cosmopolitan — and the GOP seems on the wrong side of all these trends.

The United States is the only developed country that is projected to add lots of new residents by mid-century. In 2006, the nation’s population reached 300 million. The Census Bureau estimates that the U.S. will get to 400 million by 2039. To put this growth in perspective, consider that even China (yes, China) will not add 100 million people by that date. The U.S. will gain more new residents in the next three decades than the current population of Germany — the largest European Union nation.

With each decade, more than 22 million potential new voters will enter the electorate. Parties that fix on a strategy may find that it is unworkable in just a few cycles. The Republican Party’s idea of stoking its base to gain office assumes a somewhat static voting public, which, given the dynamic nature of American demographics, is a faulty notion.

So who are most of these new people? The quick answer is both recent immigrants and their American-born offspring. By 2043, the U.S. may be a majority minority nation. Another scenario is that a high rate of intermarriage among whites and minorities may open to question the whole notion of who is “majority.” The bottom line for Republicans is that no matter how this population is defined, an increasing number of current minorities are voting for Democrats.

Republicans can, of course, switch their strategy and make more direct appeals to minority voters. As recently as 2004, President George W. Bush almost won the Latino vote. But at the moment, the Republicans seem branded as the party of white people. Furthermore, much of the Republican base — especially those listening to talk radio — believe the U.S. is being flooded with immigrants (legal and illegal). It may be hard to pivot and embrace diversity without alienating the GOP base. By contrast, many whites in the Democratic Party are comfortable with diversity and now form a transracial coalition with minority voters.

As the U.S. expands and diversifies, it is becoming more urban. The Census finds that 83 percent of Americans live in metropolitan areas and that well over half live in regions with more than 1 million residents. By other calculations, two-thirds of people added by 2040 will settle in just 20 megapolitan areas — massive urban complexes that contain more than 5 million residents.

Were just the big metro areas to vote, the presidential race would be a rout every time. The Democrats dominate major urban regions. An analysis by the Metropolitan Institute at Virginia Tech found that Barack Obama won the votes in the nation’s top 50 metro areas — often by double-digit margins.

Worse for Republicans, in 2006 and 2008, Democrats significantly expanded the areas of the metros they won. Their electoral dominance has spilled out of cities and close-in suburbs and now reaches into the kinds of sprawling subdivisions that were once reliably Republican. The suburbs in key swing states such as Colorado, North Carolina and Virginia played a particularly decisive role in delivering the presidency to Democrats.

Republicans must adjust to the demographic shifts sweeping America or risk being politically marginalized. Most significantly, the party needs to recognize that there are simply not enough rural white voters to balance the growing number of minority voters and cosmopolitan whites living in big metro areas. If Republicans think 2008 went badly, try running the same kind of small-town-flavored campaign in 2020. At that point, the vastly expanded and racially diverse metro areas in Texas and Georgia could tip those once reliably red states to the Democrats.

Robert E. Lang is co-director of the Alexandria, Va.-based Metropolitan Institute at Virginia Tech and an associate professor in urban affairs and planning at Virginia Tech’s School of Planning and International Affairs.